Scanning proton microprobe analysis of mercury and other trace elements in Fe-sulfides from a Kentucky coal

Scanning proton microprobe analysis of a series of Fe-sulfides (pyrite and marcasite) from the Manchester coal bed, Clay County, eastern Kentucky, demonstrated that Hg could be detected in some grains. The low concentration of Hg in coal, and even in the sulfides where it is generally concentrated, makes the detection difficult. Other elements, notably Ni, Cu, Zn, As, Se, Tl, and Pb, occur in greater concentrations and could be detected in more samples than Hg. All of the Fe-sulfides analyzed As substitution, and most were even more complex. Overall, there was a large variation in the amount of substitution in the sulfides. Arsenic, as an example, ranges in concentration from 11 μg/g to 12,000 μg/g in Fe-sulfides from the same coal sample. Much of the trace element concentration in this coal is in the coarse sulfides or, possibly, in other mineral phases included in the pyrite or marcasite, favorable for the pre-combustion removal of the trace elements.